Centrifuge rotor

ABSTRACT

A fixed angle centrifuge rotor is provided which can be molded from a single cavity mold with no secondary operations. The rotor includes a central hub portion and a generally frusto-conical outer portion extending downwardly and radially outwardly from the central portion for holding the tubes to be centrifuged. The frusto-conical portion is provided with a plurality of radially outwardly extending recesses, each recess being defined by radially-spaced bottom wall portions and radially-spaced top wall portions, the top wall portions being aligned with the spaces in the bottom wall portions. A tube positioned within a recess is held securely by a pair of bottom wall portions and a pair of top wall portions, but at any cylindrical cross section through the frusto-conical wall the tube is held by only a top wall or a bottom wall.

United States Patent [1 1 mg July 23, 1974 CENTRlFUGE ROTOR [75]lnventorz Donald E. Burg, Miami, Fla. [57] ABSTRACT A fixed anglecentrifuge rotor is provided which can [73] Assgnee' i g fl be moldedfrom a single cavity mold with no seconorpora vanston dary operations.The rotor includes a central hub por- [22] Filed: Dec. 17, 1971 tion anda generally frusto-conical outer portion ex- 7 tending downwardly andradially outwardly from the [21] Appl 209272 central portion for holdingthe tubes to be centrifuged. The frusto-conical portion is provided witha plurality [52] U.S. Cl. 233/26 f radially outwardly xt nding re ss s,a h r ess [51] Int. Cl B04b 9/12 being defined by radially-spaced bottomwall portions [58] Field of Search 233/26, 27, 28, 46, 16, andradially-spaced top wall portions, the top wall por- 233/21, 1 R tionsbeing aligned with the spaces in the bottom wall 1 portions. A tubepositioned within a recess is held se- [56] References Cited curely by apair of bottom wall portions and a pair of UNITED STATES PATENTS topwall portions, but' at any cylindrical cross section 3,235,173 2/1966Unger 233/26 x through the frusto'comcal wall the tube held by onlyPrimary ExaminerGeorge H. Krizmanich a top wall or a bottom wall.

v 17 Claims, 8 Drawing Figures 8A 2\5 32 I6 2a 1 CENTRIFUGE ROTORBACKGROUND AND SUMMARY This invention relates to a centrifuge rotor,and, more particularly, to a fixed angle centrifuge rotor which can bemolded by a single cavity mold without secondary operations such asdrilling or milling.

Fixed angle centrifuge rotors generally include a central hub portionfor attaching the rotor to the centrifuge and an outer tube-holdingportion for holding a plurality of generally radially extending tubes atan angle to the plane of rotation. Heretofore, the fabrication of suchrotors generally required a plurality of steps including secondary orfinishing operations such as drilling the holes for the tubes.

The invention provides a rotor which can be molded is a single operationin asingle cavity mold and does not require secondary operations. Therotor can therefore be produced very economically, and the resultantintegrally molded structure has characteristic high structuralintegrity.

DESCRIPTION OF THE DRAWING The invention will be explained inconjunction with an illustrative embodiment shown in the accompanyingdrawing, in which FIG. 1 is a top perspective view of a centrifuge rotorwhich is formed in accordance with the invention and which is holding anumber of tubes to be centrifuged;

FIG. 2 is a top plan view of the centrifuge rotor without the tubes;

FIG. 3 is an elevational view of the rotor;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 2;

' FIG. 5 is an enlarged fragmentary view of a portion of FIG. 4 showinga tube positioned in one of the tubeholding recesses of the rotor;

FIG. 6 is a bottom plan view of the rotor;

FIG. 7 is a fragmentary sectional view taken along the line 77 of FIG.4; and

FIG. 8 is a fragmentary sectional view taken along the line 8-8 of FIG.4.

DESCRIPTION OF SPECIFIC EMBODIMENT Referring now to the drawing, thenumeral 10 designates generally a centrifuge rotor having a generallycircular configuration. The rotor includes a generally circular centralhub portion 11 having a central opening 12 and a generallyfrusto-conical outer tube wall. A cylindrical attaching sleeve 17 ofmetal or other suitable material is secured within the cylindrical wall16 and provided with diametrically opposed key ways or slots 18 whichpermit the rotor to be secured for rotation with the rotary drive shaftof the centrifuge.

A cylindrical wall-or rib 20 extends generally perpendicularly upwardlyfrom the outer periphery of the hub portion and is provided with aplurality of circumferentially spaced openings 21 adjacent the hubportion. A frusto-conical wall 22 extends outwardly and downwardly fromthe cylindrical wall 20 adjacent the upper ends of the openings 21 andis interrupted by a plurality of slots, recesses, or openings 23 whichare aligned with the openings 21 and which extend parallel to the radialdirection of the rotor, i.e., the slots 23 extend in planes which passthrough the center of the hub and which extend vertically in FIGS. 3 and4. The frusto-conical wall 22 terminates at a second cylindrical wall orrib 24 which extends concentrically with the inner cylindrical wall 20and which is also provided with a plurality of circumferentially spacedopenings 25 which are aligned with the slots 23 and openings 21. Agenerally V- shaped end or outer wall 27 is connected to the bottom ofthe outer cylindrical wall 24 and includes an upwardly and outwardlyinclined frusto-conical portion 28 and a generally cylindrical outerportion 29. A generally U-shaped tube-supporting wall 30 extends betweeneach adjacent pair of the interrupted portions of the frusto-conicalwall 22 to provide a bottom support for each of the tubes. Referring toFIG. 7, eachsupporting wall 30 includes a pair of side wall portions 31which extend downwardly from the frustoconical wall 22 and an arcuatecentral or bottom wall portion 32 which extends outwardly and downwardlyrelative to the hub portion. As can be seen best in FIGS. 4 and 5, eachbottom wall 30 includes an inner end 33 which terminates slightlyoutwardly of the outer surface of the cylindrical wall 20 and an outerend 34 which terminates slightly inwardly of the inner surface of theouter cylindrical wall 24. The outer periphery of the planar wall 15 ofthe hub terminates inwardly of the inner surface of the cylindrical wall20 adjacent the openings 21 therein as at 35, and the end wall 27terminates outwardly as at 36 of the outer surface of the cylindricalwall 24 adjacent the openings 25 therein.

A plurality of tube-receiving recesses are thereby provided by the rotorin which eachU-shaped wall 30 provides longitudinally extending side andinclined bottom support for the tube and the cylindrical walls 20 and 24at the upper ends of the openings 21 and 25 therethrough provide topretaining walls. The upper ends of these openings are arcuately shapedand have inclined surfaces which extend parallel with the cylindricalouter surface of the tube 14 when supported by the bottom wall 32 formating engagement with the cylindrical tube, and each pair of side walls31 and the side portions of the openings 21 and 25 are spaced apartapproximately the diameter of the tube. The tube is thereby receivedrelatively snugly in the recess and is secured against movement in anytransverse direction. Upward movement is restrained by the cylindricalwalls 20 and24, downward movement is prevented by the bottom Wall 32,and transverse or side movement is prevented by the side walls 31 andthe sides of the openings 21 and 25. Pivotal movement of the tube isprevented by the spaced-apart top walls provided by the walls 20 and 24in cooperation with the elongated bottom wall 32. Further, in theparticular embodiment illustrated, additional bottom support for thetube is provided by the portion of the planar wall 15 of the hub whichis aligned with the axis of the tube. This portion of the planar wall 15may advantageously be beveled as at 37'to extend parallel with the outersurface of the tube to provide a slightly longitudinally extendingsupporting surface for the tube.

A tube containing material to be centrifuged may be inserted into eachrecess by inserting the tube closed end first through an opening 21 inthe inner cylindrical wall 20 at the same inclination as the bottom wall32. The tube is pushed along the bottom wall until the closed end 14athereof passes through the opening 25 and engages the inclinedfrusto-conical wall 28 (FIG. The frusto-conical wall 28 extendsgenerally transversely to the axis of the tube to provide an abutment orstop for the closed end of the tube, and the tube is thereby securedagainst outward movement under the influence of centrifugal force as therotor rotates.

I have found it advantageous to provide the inner cylindrical wall witha substantial axial extent above the frusto-conical wall 22 to protectthe inner ends of the tubes and to provide a convenient portion forgripping and lifting the rotor. However, the axial length of the wall20, the angle of inclination and the length of the tubes, and the radiusof the hub are such that each tube can be inserted and withdrawn withoutinterference from the other tubes.

Referring to FIG. 4, the rotor does not include any vertically spacedparts, i.e., parts which are spaced in the axial direction of anycylindrical cross section taken about the center of the rotor.Accordingly, it will be apparent that the rotor can be molded in asingle shot by a single cavity two-part mold, relative movement of thetwo mold parts being in the axial direction of the rotor. The rotor canthereby be molded in a single operation, and no finishing or secondaryoperation such as drilling or milling are required to provide thetube-receiving recesses. The tubular attaching sleeve 17 can bepositioned in the stationary mold half before the molding operation sothat the rotor is molded in place around the sleeve. If desired, port orrecess identification numbers or other indicia can be formed on thefrustoconical wall 22 adjacent each recess by the mold. The rotor can bemolded either from thermoplastic or thermosetting resin material or frommetal.

It is desirable to provide at least three upper and lower retainingsurfaces for the tube in any longitudinal cross section in order toprevent pivoting of the tube, two of the retaining surfaces beingpositioned on one side of the tube at spaced locations and the othersupporting surface being positioned on the other side of the tubebetween the spaced surfaces. While in the specific embodimentillustrated the tube is prevented from pivoting in a radially extendingplane by the two top retaining surfaces provided by the walls 20 and 24and the bottom retaining surface 32, it will be understood that a singletop retaining surface can be provided between a pair of spaced bottomretaining surfaces. Such a structure could still be molded in a singleoperation since the top surface would not be aligned in any cylindricalcross section with either of the bottom supporting surfaces. Although itis desirable to use at least three retaining surfaces, more may be usedif desired. For example, in the specific embodiment illustrated a fourthretaining surface is provided by the beveled portion 37 of the hub.

Although I have used specific terms in describing the various portionsof the rotor, it will be understood that the structure can be describedin other ways and various portions of the rotor can be replaced byequivalent structures. For example, the retaining surfaces for the tubeswhich are provided by the continuously extending cylindrical walls 20and 24 can be provided by relatively short cross ribs or the like whichextend only across the openings in the frusto-conical wall 22 betweenthe side walls 31. The frusto-conical wall could then be joined directlyto the outer wall 27. Also, the tenn recess is meant to include anyspace into which the tube can be inserted longitudinally and in whichthe tube is restrained against transverse movement in any direction andis not to be limited to a space which is defined by longitudinallyextending walls.

While in the foregoing specification a detailed description of aspecific embodiment of the invention was set forth for the purpose ofillustration, it is to be'understood that many of the details hereingiven may be varied considerably by those skilled in the art withoutdeparting from the spirit and scope of the invention.

I claim:

1. A molded centrifuge rotor comprising a generally circular generallyhorizontally extending central hub portion adapted to be connected to acentrifuge and an annular tube-holding portion extending outwardly fromthe hub portion, the tube-holding portion being provided with aplurality of recesses extending outwardly from the hub portion, eachrecess adapted to receive an elongated tube and being defined by a pairof opposed side walls, a bottom wall extending between the side wallsand being spaced from the hub portion, and a top wall spaced upwardlyfrom the bottom wall to permit a tube to be inserted between the topwall and the bottom wall, the top wall'extending between the side wallsin vertical alignment with the spacing between the bottom wall and thehub portion, no portion of the top wall being in vertical alignment withany portion of the bottom wall whereby a tube may be secured againsttransverse movement within each recess and the rotor may be formed inone operation by molding.

2. The rotor of claim 1 in which the hub portion is generally planar andhas top and bottom surfaces and the tube-holding portion is generallyfrusto-conical, the recesses extending radially outwardly and downwardlyfrom the hub portion at circumferentially spaced locations along theperiphery of the hub portion.

3. The rotor of claim 2 in which the bottom wall of each recess has aninner end spaced from the hub portion and an outer end, the rotorincluding a second top wall for each recess spaced upwardly from thebottom wall to permit a tube to be inserted between the second top walland the bottom wall, each second top wall extending between the sidewalls of the associated recess outwardly of the outer end of theassociated bottom wall so that no portion of the second top wall isvertically aligned with any portion of the bottom wall.

4. The rotor of claim 3 in which the end wall for each recess isprovided by a continuous generally cylindrical outer wall.

'5. The rotor of claim 1 including an end wall for each recessengageable with the outer end of a tube received by the recess forpreventing outward movement of the tube.

6. The rotor of claim 5 in which the end wall for each recess is spacedfrom the bottom wall for the recess, the rotor including a second topwall for each recess spaced upwardly from the bottom wall to permit atube to be inserted between the second top wall and the bottom wall,each second top wall extending between the side walls of the associatedrecess in vertical alignment with the spacing between the bottom walland the end wall of the associated recess, no portions of the second topwall and the bottom wall for each recess being in vertical alignment. 4

7. The rotor of claim 1 including connecting portions extending betweenthe side walls of each adjacent pair of recesses.

8. The rotor of claim 7 in which the top wall for each recess isprovided by a continuous circularly extending wall joined to the sidewalls of each recess and too said connecting portions.

9. The rotor of claim 1 in which every part which is spaced verticallyabove another part is not aligned vertically with the other part.

10. A molded centrifuge rotor comprising a generally circular generallyhorizontally extending central hub portion adapted to be connected to acentrifuge and having upper and lower surfaces and a generally annulartube-holding portion extending outwardly and downwardly from the hubportion, the tube-holding portion having a generally frusto-conical wallprovided with a plurality of openings, each opening in the frustoconicalwall extending in a vertical plane passing through the center of the hubportion, a generally U- shaped tube-supporting wall extending downwardlyfrom the frusto-conical wall at each opening therein and having an innerend spaced from the hub portion and an outer end, a pair of spaced-apartcross members extending across each opening in the frusto-conical wall,one of the cross members of each pair being positioned vertically abovethe space between the inner end of the associated tube-supporting walland the hub portion and'the other cross member of each pair being po- Isitioned outwardly of the outer end of the associated tube-supportingwall, no portion of said one cross member being in vertical alignmentwith any portion of either the associated tube-supporting wall or thehub portion and no portion of said other cross member being in verticalalignment with any portion of the associated tube-supporting wallwhereby an elongated cylindrical tube may be secured against transversemovement in each opening in the frusto-conical wall and the rotor may beformed in one operation by molding.

' 11. The rotor of claim 10 in which each of the cross members has anarcuate lower surface for mating with the other surface of a cylindricaltube.

12. The rotor of claim 10 including a generally circularly extendingouter wall spaced outwardly of said other cross members and secured tothe frusto-conical wall for preventing outward movement of the tubesbeyond the outer wall as the rotor is rotated.

13. The rotor. of claim 10 in which said one cross member of each pairis provided by a continuous generally cylindrical wall extendingupwardly from the frusto-conical wall above the inner ends of the tubesreceived by the openings.

14. The rotor of claim 10 in which said one cross members are providedby a first continuous circularly extending rib projecting upwardly fromthe frustocorlical wall and said other cross members are provided by asecond continuous circularly extending rib projecting upwardly from thefrusto-conical wall.

15. The rotor of claim 10 in which every part which is spaced verticallyabove another part is not aligned vertically with the other part.

16. A molded centrifuge rotor comprising a generally circular centralhub portion adapted to be connected to a centrifuge and an annulartube-holding portion extending outwardly from the hub portion, thetubeholding portion being provided with a plurality of recessesextending outwardly from the hub portion, each recess adapted to receivean elongated tube and being defined by a pair of opposed side retainingmeans on the tube-holding portion for restraining sideways movement ofthe tube, bottom retaining means on the tubeholding portion having aninner end spaced from the hub portion for restraining downward movementof the tube, and top retaining means on the tube-holding portionpositioned inwardly of the inner end of the bottom retaining means andoutwardly of the hub portion for restraining upward movement of thetube, no portion 'of the top retaining means being in vertical alignmentwith any portion of either the associated bottom retaining means or thehub portion whereby a tube may be secured against transverse movementwithin each recess and the rotor may be formed in one operation bymolding.

17. The rotor of claim 16 in which every part which is spaced verticallyabove another part is not aligned vertically with the other part.

1. A molded centrifuge rotor comprising a generally circular generallyhorizontally extending central hub portion adapted to be connected to acentrifuge and an annular tube-holding portion extending outwardly fromthe hub portion, the tube-holding portion being provided with aplurality of recesses extending outwardly from the hub portion, eachrecess adapted to receive an elongated tube and being defined by a pairof opposed side walls, a bottom wall extending between the side wallsand being spaced from the hub portion, and a top wall spaced upwardlyfrom the bottom wall to permit a tube to be inserted between the topwall and the bottom wall, the top wall extending between the side wallsin vertical alignment with the spacing between the bottom wall and thehub portion, no portion of the top wall being in vertical alignment withany portion of the bottom wall whereby a tube may be secured againsttransverse movement within each recess and the rotor may be formed inone operation by molding.
 2. The rotor of claim 1 in which the hubportion is generally planar and has top and bottom surfaces and thetube-holding portion is generally frusto-conical, the recesses extendingradially outwardly and downwardly from the hub portion atcircumferentially spaced locations along the periphery of the hubportion.
 3. The rotor of claim 2 in which the bottom wall of each recesshas an inner end spaced from the hub portion and an outer end, the rotorincluding a second top wall for each recess spaced upwardly from thebottom wall to permit a tube to be inserted between the second top walland the bottom wall, each second top wall extending between the sidewalls of the associated recess outwardly of the outer end of theassociated bottom wall so that no portion of the second top wall isvertically aligned with any portion of the bottom wall.
 4. The rotor ofclaim 3 in which the end wall for each recess is provided by acontinuous generally cylindrical outer wall.
 5. The rotor of claim 1including an end wall for each recess engageable with the outer end of atube received by the recess for preventing outward movement of the tube.6. The rotor of claim 5 in which the end wall for each recess is spacedfrom the bottom wall for the recess, the rotor including a second topwall for each recess spaced upwardly from the bottom wall to permit atube to be inserted between the second top wall and the bottom wall,each second top wall extending between the side walls of the associatedrecess in vertical alignment with the spacing between the bottom walland the end wall of the associated recess, no portions of the second topwall and the bottom wall for each recess being in vertical alignment. 7.The rotor of claim 1 including connecting portions extending between theside walls of each adjacent pair of recesses.
 8. The rotor of claim 7 inwhich the top wall for each recess is provided by a continuouscircularly extending wall joined to the side walls of each recess andtoo said connecting portions.
 9. The rotor of claim 1 in which everypart which is spaced vertically above another part is not alignedvertically with the other part.
 10. A molded centrifuge rotor comprisinga generally circular generally horizontally extending central hubportion adapted to be connected to a centrifuge and having upper andlower surfaces and a generally annular tube-holding portion extendingoutwardly and downwardly from the hub portion, the tube-holding portionhaving a generally frusto-conical wall provided with a plurality ofopenings, each opening in the frusto-conical wall extending in avertical plane passing through the center of the hub portion, agenerally U-shaped tube-supporting wall extending downwardly from thefrusto-conical wall at each opening therein and having an inner endspaced From the hub portion and an outer end, a pair of spaced-apartcross members extending across each opening in the frusto-conical wall,one of the cross members of each pair being positioned vertically abovethe space between the inner end of the associated tube-supporting walland the hub portion and the other cross member of each pair beingpositioned outwardly of the outer end of the associated tube-supportingwall, no portion of said one cross member being in vertical alignmentwith any portion of either the associated tube-supporting wall or thehub portion and no portion of said other cross member being in verticalalignment with any portion of the associated tube-supporting wallwhereby an elongated cylindrical tube may be secured against transversemovement in each opening in the frusto-conical wall and the rotor may beformed in one operation by molding.
 11. The rotor of claim 10 in whicheach of the cross members has an arcuate lower surface for mating withthe other surface of a cylindrical tube.
 12. The rotor of claim 10including a generally circularly extending outer wall spaced outwardlyof said other cross members and secured to the frusto-conical wall forpreventing outward movement of the tubes beyond the outer wall as therotor is rotated.
 13. The rotor of claim 10 in which said one crossmember of each pair is provided by a continuous generally cylindricalwall extending upwardly from the frusto-conical wall above the innerends of the tubes received by the openings.
 14. The rotor of claim 10 inwhich said one cross members are provided by a first continuouscircularly extending rib projecting upwardly from the frusto-conicalwall and said other cross members are provided by a second continuouscircularly extending rib projecting upwardly from the frusto-conicalwall.
 15. The rotor of claim 10 in which every part which is spacedvertically above another part is not aligned vertically with the otherpart.
 16. A molded centrifuge rotor comprising a generally circularcentral hub portion adapted to be connected to a centrifuge and anannular tube-holding portion extending outwardly from the hub portion,the tube-holding portion being provided with a plurality of recessesextending outwardly from the hub portion, each recess adapted to receivean elongated tube and being defined by a pair of opposed side retainingmeans on the tube-holding portion for restraining sideways movement ofthe tube, bottom retaining means on the tube-holding portion having aninner end spaced from the hub portion for restraining downward movementof the tube, and top retaining means on the tube-holding portionpositioned inwardly of the inner end of the bottom retaining means andoutwardly of the hub portion for restraining upward movement of thetube, no portion of the top retaining means being in vertical alignmentwith any portion of either the associated bottom retaining means or thehub portion whereby a tube may be secured against transverse movementwithin each recess and the rotor may be formed in one operation bymolding.
 17. The rotor of claim 16 in which every part which is spacedvertically above another part is not aligned vertically with the otherpart.